i18n: ~310 keys per locale missing — whole features silently render in English

`en.json` has 1530 leaf keys; es/ja/ko/zh each miss 309 and fr misses 312 (1,548 key-locale pairs). The fallback merge (`src/intl/LocaleContext.tsx:160`, `fallbackLocale="en"`) makes this invisible — missing keys silently render English, which is the top user complaint about mixed languages. Clusters: `whats_on_admin.*` (66/locale), `component.jump.*` (24), `component.creators_landing.*` (18), `page.creator-hub.*` (17).

Additionally ~100-134 values per locale are byte-identical to English; sampling suggests roughly half are legit (brand/format strings like "DAO", "{x},{y}") and half genuinely untranslated (e.g. `create_event.rejected_alert`, `page.download.download_for_short`).

Suggested process: generate a per-locale key-diff worklist (flatten en vs locale; emit key + English source) as translator input; re-run post-merge to confirm zero diff. No code change needed.